The present invention relates to an actuator, and more particularly, to a fluidly driven actuator which comprises a solenoid control valve and a diaphragm, the diaphragm being determined in its position by fluid pressure controlled by the solenoid control valve.
One example of this kind actuator is disclosed in this Japanese Patent Application No. 34268/1983. This actuator is used in a vehicle speed controller adapted to store a speed of the vehicle for maintaining the vehicle speed at the stored one in an automatic manner.
An electrical circuitry of the vehicle speed controller is shown in FIG. 1. Referring to FIG. 1, an electronical control device 10 is composed of a single chip microcomputer CPU and interface circuits. An runaway detecting circuit 20 is connected to a reset port RESET of the CPU. A vehicle speed detecting lead switch SW2, a clutch switch SW3, a stop switch SW4, a set switch SW5 and a resume switch SW6 are respectively connected to an external interrupt input port IRQ and input ports K.sub.2, K.sub.3, K.sub.0 and K.sub.1 through interface circuits IF1, IF2, IF3, IF4 and KF5.
In the vicinity of the vehicle speed detecting lead switch SW2 there is arranged a permanent magnet connected to a speed meter cable (not shown), so that the contact of the vehicle speed detecting lead switch SW2 is opened and closed as the permanent magnet rotates upon movement of the vehicle. When the contact of the SW2 is changed from the closed state to the opened state, an output level of the interface circuit IF1 assumes a low level L and the microcomputer CPU receives an interrupt demand.
The clutch switch SW3 is opened and closed in interlock relation with a clutch pedal of the vehicle, while the stop switch Sw4 is opened and closed in interlock relation with a brake pedal. To the stop swtich SW4 is connected a stop lamp STL which is lit up in the ON (closed) state of the SW4.
Both the set switch SW5 and resume switch SW6 are of push botton switches and disposed on an instrument panel in such positions as convenient for the driver to operate them.
An output port O.sub.0 of the microcomputer CPU is connected to the runaway detecting circuit 20, and output ports O.sub.2 and O.sub.3 thereof are connected to solenoid drivers DV1 and DV2, respectively. To an output of the solenoid driver DV1 is connected a negative pressure control solenoid SL.sub.1 of a later-described actuator (100), while to an output of the solenoid driver DV2 is connected a negative pressure release solenoid SL.sub.2 thereof.
The voltage from a vehicular battery is applied via an ignition key switch SW1 to the negative pressure control solenoid SL.sub.1, the negative pressure release solenoid SL.sub.2, and a constant-voltage power supply circuit 30 for producing a constant voltage Vcc. A circuit 40 denotes an interrupt driver for use in energyzing the negative pressure release solenoid SL.sub.2 independently of operation of the CPU, when the brake is effected.
FIG. 2 shows a construction of an actuator 100 controlled by the electrical circuitry shown in FIG. 1. Referring now to FIG. 2, a housing 101 mainly comprises a housing base 101a and a housing cover 101b. A diaphragm 102 is held between confronting flange portions of the base 101a and the cover 101b so as to divide an internal space of the housing 101 into two chambers. A first internal space 11a defined by the diaphragm 102 and the housing base 101 serves as negative pressure chamber, and a second internal space 11b defined by the diaphragm 102 and the housing cover 101b is communicated with the atmosphere through an opening of the housing cover 101b. A compression coil spring 103 is accommodated in the second internal space 11b. The spring 103 is interposed between a holder plate 12 for supporting the valve device and the diaphragm 102. When the pressure in the negative pressure chamber 11b is near atmospheric pressure, the spring 103 pushes the diaphragm 102 in a direction in which the second internal space 11 b is narrowed and brings it into a position substantially indicated by phantom lines. A rod 104 fixed to the nearly central part of the diaphragm 102 extends to penetrate through the housing cover 101b. A link of a throttle valve 105 is operatively connected to the rod 104. The housing base 101a is formed with a negative pressure intake port 107 in communication with an intake manifold 106, as well as atmosphere intake ports 108 and 109.
Designated at the reference numeral 110 is a negative pressure control valve and at 111 is a negative pressure release valve, both valves being supported by the holder plate 12 fixed to the housing 101a. A movable piece 112 of the negative pressure control valve 110 is tiltable about P, and it has one end connected to an extension coil spring 113 and the other end located opposite to the control solenoid SL.sub.1. Both ends of the movable piece 112 function as valve bodies which, in response to energization or deenergization of the solenoid SL.sub.1, cause the negative pressure intake port 107 to be opened and the atmosphere intake port 108 to be closed (the state illustrated) or cause the negative pressure intake port 107 to be closed and the atmosphere intake port 108 to be opened.
The negative pressure release valve 111 is also supported by the holder plate 12 and comprises, similarly to the negative pressure control valve 110, a movable piece 114, an extension coil spring 115 and the solenoid SL.sub.2. In response to energization or deenergization of the SL.sub.2, the movable piece 114 makes the atmosphere intake port 109 closed (the state illustrated) or open, respectively. Incidentially, designated at 116 is an accelerator pedal, and at 117 is an extension coil spring.
The conventional actuator is constructed as stated above and driven by the electronical control device 10 as shown in FIG. 1.
Control operation of the microcomputer CPU in FIG. 1 is shown in FIGS. 3a, 3b, 3c, 3d and 3e. By referring to these figures, the operation of the CPU will be explained in order. It is to be noted that, when the vehicle moves, the lead switch SW2 always repeats its ON/OFF operation and the microcomputer CPU executes the external interrupt processing as shown in FIG. 3d at each time the SW2 is turned OFF.
First, turning-on of the power effects the initial setting. That is, the output ports are set at their initial levels and the content of each memory is cleared.
The level of the output port O.sub.0 is inverted. That is, the level of the port O.sub.0 is set at a low level L when it was set at a high level H, and is set at a high level H when it was set at a low level L. This processing is to be surely executed once within a predetermined time if the CPU is under the normal operation, whereby a pulse signal of almost constant period is applied to the runaway detecting circuit 20 from the CPU. When the pulse signal is applied, the runaway detecting circuit 20 sets an output level of a comparator CP at H and turns a transistor Q1 ON, thus causing a RESET terminal of the CPU to assume a high level H. If the CPU should make a runaway or the like and produce no pulse at the port O.sub.0, the output level of the comparator CP is inverted to L, so that the transistor Q1 is turned OFF and a low level L is applied to the reset terminal RESET of the CPU. When the reset terminal RESET assumes L, the CPU performs the same operation as that at the time of power-off. As a result, such a runaway is surely stopped.
Under the normal operation, the CPU reads levels of the input ports K.sub.0, K.sub.1, K.sub.2, K.sub.3, etc., and it judges operations of the switches or the like and then executes the processing in accordance with the judged switch operations as follows.
In case there is no change in the inputs (except for the case any of timers, flags, etc. is set), the CPU executes the processing loop passing through the steps S2-S3-S4-S42-S43 and then returning back to the step S2 after execution of plural stored routines as shown in FIG. 3c. In this case, the content of a vehicle speed memory, a target value register, flags, etc. remains unchanged.
When the clutch switch SW3 or the stop switch SW4 is turned ON, or when the vehicle speed is lowered less than a predetermined value (e.g., 30 km/h), the level of the output port is set in a direction where the solenoid is not energized, and the content of the target value register R0 is cleared to release the constant-speed control. Also, flags or the like are all cleared. This releases the constant-speed traveling mode when it was set. In addition, the release solenoid SL.sub.2 is so deenergized that the negative pressure actuator 100 is operated in a direction where it closes the throttle valve quickly. Subsequently, the CPU proceeds to the step S61 and then returns back to the step S2 after passing through the plural stored reutines.
When the set switch SW5 is turned ON for the first time, it proceeds to the steps S9-S17-S18-S19-S20, whereby a set-on flag SET-ON is set at "1" and the control solenoid controlling duty is set at 5%. Since the control solenoid controlling duty of 5% increases a time rate in which the negative pressure control valve 110 causes the interior of the negative actuator 100 to be communicated with the atmosphere, the negative actuator 110 is moved in a direction where it closes the throttle valve, thus resulting in that the vehicle speed is lowered with the lapse of a time. Actual driving of the control solenoid is performed in accordance with the set duty. In the state that the set switch SW5 is pushed down, the CPU proceeds to the steps S61-S62-S81, . . . while passing through the plural stored routines and further proceeds to the steps S2-S3, . . . S9-S17-S18-S61.
When the set switch SW5 is turned OFF, the CPU proceeds to the steps S9-S10-S11-S12-S13-S14, whereby the set-on flag SET-ON is cleared (0) and a set-off flag SET-OFF is set at 1. Subsequently, it comes into the step S61 and now proceeds to the steps S67-S68-S69-S70-S80, . . . because the set-off flag SET-OFF is 1, whereby the content of a counter (pointer) RA for specifying the vehicle speed memory is incremented (within a value not greater than 3) and a one-second time for setting is cleared and started. After completion of this processing, the set-off flag SET-OFF is cleared to "0". In other words, execution of the steps S67, S68, S69 and S79 is effected in the first processing timing only where the set switch SW5 was turned OFF. From the next time, it proceeds to the steps S61-S62-S63, . . .
When the set switch SW5 is not turned ON even after the lapse of 1 second from its turning-off, it is detected in the step S63 that the preset time has been out and then the operation is forwarded to S64-S65-S66. Whereby, the content of the target value register R0 is stored into the vehicle speed memory which is specified by the content of the counter RA, a later-described throttle initializing routine is executed and then an operating mode is set to the constant-speed control mode.
On this occasion, since the target value register R0 memories therein a vehicle speed at the time of execution of the step S14, i.e., at the moment when the set switch SW5 was turned OFF, the then vehicle speed is stored into the predetermined memory. When the set switch SW5 repeats its ON/OFF operation two time until it finally comes into the OFF state (1-second turning-off), the processing step of S67-S68-S69-S70 is executed two times during such a period, so that the content of the counter RA becomes 2 and hence the content of the target value register R0 is memorized into the second vehicle speed memory. Since the number of vehicle speed memories is three in this embodiment, the step S67 is provided to prevent the value of the counter RA from exceeding 3). Therefore, even when the set switch SW5 is turned ON/OFF continuously more than three times, the third vehicle speed memory is selected in any case.
Coming into the constant-speed control mode, the CPU proceeds to the steps S40-S41-S42 thereby to repeatedly set the control solenoid controlling duty for each execution of this processing so that the content of the target value register R0, i.e., the memorized vehicle speed becomes equal to the actual vehicle speed. If the set switch SW5 is held in the pushed state, it is continued such a condition that the controlling duty was set at 5% in the step S20, as a result of which the vehicle speed is lowered gradually.
When the resume switch SW6 is turned ON for the first time, the CPU proceeds to S31-S44-S45-S46-S47-S48-S43, whereby a resume-on flag RESUME-ON is set to "1" and 0.9-second resume time is cleared and started. Subsequently, it executes the processing loop of S61, . . . S81-S82-S2. If the resume switch SW6 is held in the pushed (ON) state for 0.9 second, the step 48 detects that the preset time has been out, and the operation is forwarded to the step S49 where the control solenoid controlling duty is set at 90%. Since the control solenoid controlling duty of 90% increases a time rate in which the negative pressure control valve 110 causes the interior of the negative pressure actuator 100 to be communicated with a negative pressure source (intake manifold), the negative pressure actuator 110 is moved in a direction where it opens the throttle valve with the lapse of a time. As a result, the vehicle speed is increased.
When the resume switch SW6 is turned OFF, the CPU first proceeds to the steps S31-S32-S33-S34-S35-S36, . . . whereby the resume-on flag RESUME-ON is cleared to "0" and a resume-off flag RESUME-OFF is set to "1". If the resume switch SW6 continues to be turned ON for a long time and the 0.9-second timer is timed out, the CPU then proceeds to S36-S37-S38-S39, so that, similarly to that of the ON/OFF operation of the set switch SW5, the present vehicle speed is stored in the target value register R0 and the content of the target value register is memorized in the vehicle speed memory which is specified by the RA. Also, the resume-off flag RESUME-OFF is cleared to "0" to prevent that the normal resume operation will not be performed in the plural stored routines.
If the resume switch SW6 is turned OFF before the 0.9-second timer will be timed out, the CPU proceeds to S81-S87-S88-S89-S90 because the resume-off flag RESUME-OFF is "1", whereby the content of the counter RA is incremented, the 1-second resume timer is cleared and started, and the resume-off flag RESUME-OFF is cleared to "0". The processing step of S81-S87-S88-S89-S90 is executed once during the time the resume-off flag RESUME-OFF assumes "1", i.e., every when the resume switch is changed from the ON state to the OFF state. Thus, the number of times that the resume switch SW6 has been changed from the ON state to the OFF state, is memorized in the counter RA.
When one second has lapsed from turning-off of the resume switch SW6, the CPU proceeds to S81-S82-S83-S84-S85-S86 because the 1-second resume timer is timed out, whereby the content of the vehicle speed memory specified by the content of the counter RA, e.g., the content of the third vehicle speed memory in case the resume switch SW6 repeats its ON/OFF operation three times, is stored in the target value register R0. Then, the throttle initialization routine S86 is executed and the constant-speed control mode is set. Coming into the constant-speed control mode, the CPU proceeds to the steps S40-S41-S42-S43, whereby the control solenoid controlling duty is updated so that the present vehicle speed approaches the content of the target value register.
The throttle initialization routine will now be described by referring to FIG. 3e. Briefly stated, this processing is to perform the estimated control (open loop control) for the purpose of quickly driving the negative actuator 100 into a predetermined position (throttle initial opening degree position). More specifically, the control solenoid controlling duty is set at a high value (90%) and a time period to be continued to hold this time is previously calculated in accordance with the content of the target value register R0. This calculated time is set in a timer and the 90% duty control is continued until the preset time is timed out. When timed out, a flag indicating the progress of constant-speed control is set to effect the constant-speed mode.
The external interrupt processing will now be described by referring to FIG. 3d. This processing is to obtain the ON/OFF period of the vehicle speed detecting lead switch SW2. Every when this processing is executed or the SW2 is turned OFF, the counted value of an internal timer is read and then the time is cleared and restarted. If the counted value of the timer is above a predetermined value (i.e., the vehicle speed is below a predetermined level), a low-speed flag is set. When the low-speed flag is set, the CPU proceeds from the step S8 in the main routine to the branched step S15, whereby the constant-speed control speed is released in a similar manner as that when the clutch pedal or the brake pedal is operated.
In the prior art as mentioned above, the electronical control device 10 (FIG. 1) and the actuator 100 (FIG. 2) are constituted separately and arranged on the vehicle dispersedly.
On the other hand, since automatization of vehicles has been advanced and a larger number of various devices are required to be arranged thereon in recent years, there is increased a demand for reduction in the mounting space and the cost. It may be, therefore, proposed to incorporate the actuator and the electronical control circuit into the unitized form. But this method accompanies with a problem of heat-resistant temperature of semiconductor elements used in the electronical control device, because the actuator is disposed in an engine room of the vehicle and the room has a relatively high atmospheric temperature. In other words, since the heat-resistant temperature of semiconductor elements is generally low, it is difficult to mount them directly onto the actuator. Alternatively, semiconductor elements with high heat-resistance may be used to realize such direct mounting, but this results in another problem of the increased cost.